Adde slimerjs support to JS tests

This commit contains 16 more, squashed commits:

Added slimerjs flag

Fixed some bugs with flag code

Figured out how to add arg correctly

Cleanup

Improvements to the test framework for FF

Log to see if slimmer is actually running

Added print in controller to debug

Added full logging to casperjs

Remove the special logging logic since it was caussing a failure

remove notebook.dirty = false line in favor of
overwritting onbeforeunload.

Capture output for slimerjs

Fixed iptestcontroller rebase issues

Fixed rebase issues.

Wait for notebook to load completely before testing

Fixed stdout capture for slimerjs tests.

Clean-up comments in util.js

Added slimerjs to Travis

Fixed indent .travis.yml

Comment out slimerjslauncher env var.

Removed zmq flag which doesn't work there anyways,
it was added by me in a recent commit

Fixed travis yaml,

broken because of rebase
Fixed image test for slimerjs
Fix isolated svg color tests so 'rgb()' colors are accepted
Make notebook tests play nicely with SlimerJS
- notebook/dualmode_markdown.js
- notebook/safe_append_output.js
Make int widget tests play nicely with slimer
Added slimer support for py3.x
Fix for xvfb SlimerJS environment.
Some cleanup
Make a nice assert function for properly testing locale specific colors.
Moved is_cell_rendered into base
Add slimerjs flag to test engine.
Fixed spaces in ipcontroller
Fixed typo in util.js,

resulted from moving is_cell_rendered into util.js
Rebase fix(es)
Address comments
Re-add print
Better integrate output from slimerjs tests
Merge pull request #21 from takluyver/slimerjs

Better integrate output from slimerjs tests
Merge pull request #5323 from jdfreder/slimerjs

Add support for Firefox JS testing